Re: [PATCH -tip] compiler_types.h: Optimize __unqual_scalar_typeof compilation time

From: Arnd Bergmann
Date: Wed May 27 2020 - 08:31:27 EST

On Wed, May 27, 2020 at 1:36 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> On Wed, May 27, 2020 at 1:27 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > On Wed, May 27, 2020 at 12:33 PM Marco Elver <elver@xxxxxxxxxx> wrote:
> >
> > This gives us back 80% of the performance drop on clang, and 50%
> > of the drop I saw with gcc, compared to current mainline.
> >
> > Tested-by: Arnd Bergmann <arnd@xxxxxxxx>
> >
> Hi Arnd,
> with "mainline" you mean Linux-next aka Linux v5.8 - not v5.7?

I meant v5.7.

> I have not seen __unqual_scalar_typeof(x) in compiler_types.h in Linux v5.7.
> Is there a speedup benefit also for Linux v5.7?
> Which patches do I need?

v5.7-rc is the baseline and is the fastest I currently see. On certain files,
I saw an intermittent 10x slowdown that was already fixed earlier, now
is more like 2x slowdown for me and 1.2x with this patch on top, so we're
almost back to the speed of linux-5.7.